One of the most persistent and troublesome problems arising during modern fabric laundering operations is the tendency of some colored fabrics to release dye ("fugitive dye") into the laundering solutions. The dye is then transferred onto other fabrics being washed therewith. Dye transfer occurs, to a greater or lesser extent, in most loads. It is not only a problem in the disastrous situation when the entire load turns pink or blue. It is present at low insidious levels virtually all the time, contributing to what is seen as dinginess on whites, dullness on colours or just cleaning. Dye transfer is also one of the users' most important concerns: a solution to the problem is one of their most often mentioned unmet needs.
One way of overcoming this problem would be to bleach the fugitive dyes washed out of dyed fabrics before they have the opportunity to become attached to other articles in the wash.
Suspended or solubilized dyes can to some degree be oxidized in solution by employing known bleaching agents.
GB 2 101 167 describes a stable liquid bleaching composition containing a hydrogen peroxide precursor which is activated to yield hydrogen peroxide on dilution.
However, it is important at the same time not to bleach the dyes actually remaining on the fabrics, that is, not to cause color damage.
U.S. Pat. No. 4,077,768 describes a process for inhibiting dye transfer by the use of an oxidizing bleaching agent together with catalytic compounds such as iron porphins.
U.S. patent application Ser. No. 421,414 describes peroxidases and oxidases utilized for the oxidation of organic or inorganic substances, including colored substances.
A dye transfer inhibiting composition comprising an enzymatic system capable of generating hydrogen peroxide and iron catalysts has been disclosed in copending EP Patent Application 91202655.6, filed Oct. 9, 1991.
EP 424 398-A describes a detergent additive capable of exerting a bleaching effect comprising a peroxidase. The additive further comprises one or more enzymes, particularly a lipase, protease, amylase or a cellulase.
Peroxidase is a bleaching enzyme which was proposed for dye transfer inhibition in detergent applications. The enzyme induces dye transfer inhibition via oxidation of bleeding dyes in solution. To achieve good dye bleaching an accelerator is required. Current peroxidase/accelerator technology systems only provide performance at pH levels below 8. This was a major limitation for the implementation of this technology in high pH detergents. An accelerator system based on phenothiazine 10-propionic acid was identified which allows the peroxidase to provide performance in high pH detergent: applications. It has now been surprisingly found that this system works exceptionally well in a formulation containing anionic surfactant, especially alkyl sulphate compositions without linear alkylbenzenesulfonate.
It is therefore an object of the present invention to provide dye transfer inhibition systems or detergent compositions containing such dye transfer inhibition system which exhibit optimum dye transfer inhibition in wash solutions by using said peroxidase in conjunction with a phenothiazine accelerator in the presence of anionic surfactant while the detergent composition is free of linear alkylbenzenesulfonate (LAS).
The anionic surfactant can be any sulfate or sulphonate based surfactant for detergent, like alkylsulfate. Preferred is an alkylsulfate containing an alkyl chain length between C.sub.8 -C.sub.20. Alternative combinations are for instance ethoxylated alkyl sulfates in combination with alkyl sulfates. The ethoxylation degree is preferably from 1 to 50.
Addition of nonionic surfactant especially ethoxylated nonionic surfactants and/or fatty acid amide surfactants exhibits even a more pronounced dye transfer inhibition effect during the wash.
The nonionic surfactant consists of alkyl chains of C8-C20 and preferably ethoxylate groups with 1 to 50 monomer units. Also preferred is fatty amide surfactants like the C.sub.10 -C.sub.18 N-alkyl polyhydroxy fatty acid amides. Typical examples include the C12-C18 N-methylglucamides (see WO 92/06154). Preferred levels of nonionic surfactants is 2-15% in finished product. According to another embodiment of this invention a process is also provided for laundering operations involving colored fabrics.